Research shows sentinel nodes accurately pinpoint cancer

Dr. Kathryn Verbanac. Photo by Cliff Hollis

GREENVILLE, N.C.
(Oct. 1, 2002)
—
A less invasive technique for detecting breast cancer's spread continues to produce impressive accuracy in determining the extent of disease, according to an East Carolina University researcher who presented interim data during the "Era of Hope" Department of Defense Breast Cancer Research Program meeting Sept. 25-28 in Orlando, Fla.

Dr. Kathryn Verbanac, associate professor of surgery at the Brody School of Medicine at ECU, and Dr. Lorraine Tafra, director of the Anne Arundel Medical Center Breast Center in Annapolis, Md., and formerly an oncology surgeon at ECU, have received $2.4 million in grants since 1998 from the Department of Defense breast cancer research program to study the technique known as sentinel node biopsy.

The biennial "Era of Hope" research meetings bring together researchers in different fields to share their ideas and identify promising new directions for breast cancer research.

Tafra and Verbanac presented interim results from an ongoing four-year trial during the meeting. They reported on new data that support expanding the pool of women with breast cancer who are potential candidates for SNB, a less-invasive procedure to determine whether the disease has spread to the lymph nodes. The study also provides evidence that the type of diagnostic test concluded on the SNB sample may improve the accuracy of the results.

"Sentinel node biopsy is dramatically better than axillary node dissection as it is less invasive and more accurate for finding tumor spread," said Tafra. "This, and other, multi-center studies have shown that the surgeon's experience with the procedure is critical. Now we're investigating the role of other factors that might widen the applicability of the technique and may further improve reliability."

SNB is replacing axillary node dissection as the procedure of choice among recently diagnosed patients to determine whether cancer has migrated beyond the breast, and thus whether post-surgical treatment is warranted and what type of treatment is appropriate. With axillary dissection, 10-30 lymph nodes under the arm next to the affected breast are removed in a procedure that involves dissection around nerves and the nearby major vein. The rate of complications - primarily fluid collection, infection and loss of sensation in the arm - can be as high as 25 to 50 percent. However, only a few of these axillary lymph nodes actually drain from the breast and are appropriate first-line indicators of metastatic disease - or disease that has spread. Most women have one or two such "sentinel" nodes.

With SNB, the surgeon injects one or more agents around the tumor. The agents travel through the lymphatic system, highlighting the sentinel nodes most likely to contain metastatic disease; no major nerves or vessels are disturbed. If the sentinel nodes do not contain disease, the chance of having disease in the remaining lymph nodes should be very small.

In this study, scientists compared SNB results from more than 650 patients who had SNB accompanied by the standard axillary node dissection procedure to see whether they could identify any patient-specific factors that might be related to "false-negative" SNB readings - those that miss cancer in the sentinel node when it is present in another axillary node. The study found no association between a false-negative SNB reading and several factors including patient age, tumor type or location, multiple versus single cancer sites in the breast, or preoperative chemotherapy. This data has opened the door to this valuable procedure to thousands of women previously thought not to be candidates for the procedure, Tafra said.

"There will be only a small percentage of patients, less than 1 percent, for whom the sentinel node will not be an accurate reflection of the remaining lymph nodes," Tafra said. "Why this occurs, even in experienced hands, remains a mystery." However, it rema